The land the partners cultivated was semi-arid former dry forest, not ideal for growing sugarcane, a crop that required much water. Samuel Alexander realized that rain was plentiful miles away in the rainforests on the windward slopes of Haleakalā mountain. Thus, he designed a 17-mile (27 km) long irrigationaqueduct that diverted water from that part of Haleakalā to their plantation. Work started on the aqueduct in 1876 and was completed two years later in 1878.

After completion of the aqueduct, the company grew and was eventually renamed Alexander & Baldwin Plantation. Between 1872 and 1900, the company gradually took over more land and sugar mill operations. In 1898, Alexander and Baldwin purchased a controlling interest in one of its rival companies, Hawaiian Commercial & Sugar Company (HC&S) from Claus Spreckles.[2] By 1899, the company had bought out Maui’s two main railroad lines (Kahului Railroad Company and Maui Railroad & Steamship Company). In 1900, the company incorporated and was renamed Alexander & Baldwin, Ltd.

Following incorporation, the company continued to prosper. It came to be one of Hawaii’s Big Five companies which held a virtual oligarchy over Hawaii’s economy during the region’s territorial years. In this period, the company entered many new businesses and controlled more than 100,000 acres (40,000 ha) of land in the Territory.

In 1905, Alexander & Baldwin and other Big Five companies took control of the California and Hawaiian Sugar Company (C&H), giving Alexander & Baldwin a factory where they could refine its sugar.

Over the following decades, the company opened or bought out sugar operations at Puʻunene, Kahuku, and Kauaʻi island as well as pineapple operations on Maui and Kauaʻi. In 1908, the company bought a portion of the Matson Navigation Company, a major shipping line operating in the territory. The company sold its sugar interests on Kauaʻi and consolidated all of its Maui operations into an enlarged Hawaii Commercial & Sugar Company in the 1930s while continuing its pineapple operations as well as its sugarcane plantation in Kahuku until the 1960s.

Following World War II, the company entered a new business: land development and real estate. The company formed a new subsidiary, the Kahului Development Co., to develop housing in the Kahului area. In the following years, the company became more involved in the development of its land and the Kahului Development Co. became A&B Properties, Inc.

In 1962, the company purchased all outstanding interests in the Hawaii Commercial & Sugar Company and the sugar operation became wholly owned by Alexander & Baldwin. In 1964, the company also bought out the interests in Matson Navigation Company held by three of its fellow "Big Five" competitors: American Factors, C. Brewer & Co., and Castle & Cooke. In 1969, the company purchased all remaining, outstanding shares in Matson and the shipping company became a wholly owned subsidiary of Alexander & Baldwin.

In recent decades, the company’s development and real estate division has grown as A&B Properties developed new residential and commercial projects on other land the company owned. In addition, Alexander & Baldwin entered diversified agriculture, beginning to cultivate coffee and macadamia nuts in the 1980s.

On January 6, 2016 Alexander & Baldwin announced plans to transition out of sugar farming on Maui by the end of the year, discontinuing the Maui Sugar brand and ceasing production of sugar at the last remaining plantation on the Hawaiian islands.[4]

Alexander & Baldwin has drawn repeated criticism from Maui residents over the use of pre-harvest field burning by its subsidiary Hawaiian Commercial & Sugar Company. HC&S cultivates approximately 35,000 acres of sugarcane on Maui, with roughly 400 acres per week being burned from March to November each year to remove dried leaves from the cane before it is harvested and processed.[7] A spokesman for HC&S claimed that "burning, in the field, is the only economical means HC&S has found to-date of removing the dried leafy material from its crop."[8] Maui environmentalists and physicians have countered by asserting that the burning process has caused increased rates of asthma and respiratory disease, especially among children, released carcinogens from burning PVC pipes used in the irrigation system,[7] and resulted in highway closures and car crashes.[9][10] Community organizers have called on A&B to replace burning with green harvesting methods,[11] and in 2012, presented the Hawaii Department of Health with a petition signed by 8,700 Maui residents, asking it to deny the company a burning permit for the coming year.[12]

The company's Puunene Mill has also attracted criticism from residents, who have pointed out that its equipment does not meet federal emissions standards and that its high coal consumption produces unsafe levels of sulfur dioxide.[13]

Some activists have reported receiving threats from or being assaulted by HC&S employees and members of the International Longshore and Warehouse Union, which has been active in lobbying for continued cane burning on behalf of Alexander & Baldwin.[7][10]

The company's agricultural practices, as well as its history and the careers of its missionary founders, were satirized by Maui author Tim Parise in the novel Totum Hominem.[14]